U.S. patent application number 16/566539 was filed with the patent office on 2020-03-12 for liquid crystal display.
The applicant listed for this patent is Samsung Display Co., Ltd.. Invention is credited to Yeon Cu KIM, Israel Esteban LAZO MARTINEZ, Ki Chul SHIN.
Application Number | 20200081302 16/566539 |
Document ID | / |
Family ID | 69719125 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200081302 |
Kind Code |
A1 |
KIM; Yeon Cu ; et
al. |
March 12, 2020 |
LIQUID CRYSTAL DISPLAY
Abstract
A liquid crystal display includes: a liquid crystal panel
including a liquid crystal layer, a pixel electrode, and a common
electrode; and a backlight unit including a light source to provide
light to the liquid crystal panel. The pixel electrode includes a
longitudinal electrode having a bar shape and extending in a
vertical direction; a transverse electrode having a bar shape,
crossing the longitudinal electrode, and extending in a horizontal
direction; and a branch electrode having a bar shape, extending
from the longitudinal or transverse electrode, and including an
oblique part extending in an oblique direction. The common
electrode overlaps the longitudinal electrode, and a longitudinal
opening extending in the vertical direction is defined in the
common electrode, and a width of a part of the pixel electrode
where the longitudinal and the transverse electrodes cross each
other is substantially the same as a width of the transverse
electrode.
Inventors: |
KIM; Yeon Cu; (Yongin-si,
KR) ; LAZO MARTINEZ; Israel Esteban; (Hwaseong-si,
KR) ; SHIN; Ki Chul; (Seongnam-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Display Co., Ltd. |
Yongin-si |
|
KR |
|
|
Family ID: |
69719125 |
Appl. No.: |
16/566539 |
Filed: |
September 10, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/133707 20130101;
G02F 1/163 20130101; G02F 1/133528 20130101; G02F 2201/40 20130101;
G02F 2001/134318 20130101; G02F 2001/1635 20130101; G02F 1/134309
20130101; G02F 1/134336 20130101 |
International
Class: |
G02F 1/1343 20060101
G02F001/1343; G02F 1/1337 20060101 G02F001/1337; G02F 1/1335
20060101 G02F001/1335; G02F 1/163 20060101 G02F001/163 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2018 |
KR |
10-2018-0108355 |
Claims
1. A liquid crystal display comprising: a liquid crystal panel
including a liquid crystal layer, a pixel electrode, and a common
electrode; and a backlight unit including a light source, wherein
the backlight unit provides light to the liquid crystal panel,
wherein the pixel electrode includes: a longitudinal electrode
having a bar shape and extending in a vertical direction; a
transverse electrode having a bar shape, crossing the longitudinal
electrode, and extending in a horizontal direction; and a branch
electrode having a bar shape, extending from the longitudinal
electrode or the transverse electrode, and including an oblique
part extending in an oblique direction with respect to the
longitudinal electrode or the transverse electrode, wherein the
common electrode has a longitudinal opening overlaping the
longitudinal electrode of the pixel electrode, and extending in the
vertical direction, and a width of a part of the pixel electrode
where the longitudinal electrode and the transverse electrode cross
each other is substantially the same as a width of the transverse
electrode or a width of the longitudinal electrode.
2. The liquid crystal display of claim 1, wherein the pixel
electrode further includes an edge transverse electrode having a
bar shape, extending in the horizontal direction, and connected to
an end of the longitudinal electrode.
3. The liquid crystal display of claim 2, wherein the edge
transverse electrode is connected to an end of the branch
electrode.
4. The liquid crystal display of claim 3, wherein the oblique part
of the branch electrode forms an angle in a range of about 60
degrees to about 80 degrees with the transverse electrode.
5. The liquid crystal display of claim 4, wherein the common
electrode further comprises a notch opening having a width extended
at the longitudinal opening.
6. The liquid crystal display of claim 5, wherein the notch opening
overlaps the part where the longitudinal electrode and the
transverse electrode cross each other.
7. The liquid crystal display of claim 1, wherein the pixel
electrode further includes an edge longitudinal electrode having a
bar shape, connected to an end of the transverse electrode, and
parallel to the longitudinal electrode.
8. The liquid crystal display of claim 1, wherein the pixel
electrode further includes an edge longitudinal electrode having a
bar shape and parallel to the longitudinal electrode, and the edge
longitudinal electrode is connected to an end of the branch
electrode and is not connected to the transverse electrode.
9. The liquid crystal display of claim 1, wherein the branch
electrode further includes a part parallel to the transverse
electrode or the longitudinal electrode, thereby defining a bent
structure with the oblique part.
10. The liquid crystal display of claim 1, wherein the common
electrode further comprises a notch opening having a width extended
at the longitudinal opening is defined in the common electrode, and
the notch opening overlaps the part where the longitudinal
electrode and the transverse electrode cross each other.
11. The liquid crystal display of claim 10, wherein the notch
opening extends to be parallel to the transverse electrode.
12. The liquid crystal display of claim 1, wherein the pixel
electrode includes a first pixel electrode and a second pixel
electrode adjacent to each other, the liquid crystal panel further
includes a first gate line, a second gate line, a first data line,
a second data line, a first thin film transistor, and a second thin
film transistor, the first thin film transistor is connected to the
first pixel electrode and connected to the first gate line and the
first data line, and the second thin film transistor is connected
to the second pixel electrode and connected to the second gate line
and the second data line.
13. The liquid crystal display of claim 12, wherein the first gate
line and the second gate line receive a same gate signal as each
other.
14. The liquid crystal display of claim 13, wherein the first pixel
electrode and the second pixel electrode are arranged along an
extending direction of the first data line and the second data
line, and the first data line and the second data line are disposed
to cross the first pixel electrode and the second pixel electrode,
respectively.
15. The liquid crystal display of claim 1, wherein the liquid
crystal panel further includes an upper polarizer and a lower
polarizer attached at both sides thereof, respectively.
16. The liquid crystal display of claim 15, wherein the backlight
unit further includes a prism sheet disposed under the liquid
crystal panel and a reflection sheet disposed under the prism
sheet, and the prism sheet has a prism hill, and the prism hill is
disposed toward the reflection sheet.
17. The liquid crystal display of claim 16, wherein an extending
direction of the prism hill is the same as a short side direction
of the liquid crystal panel, and a prism hill extending in a long
side direction of the liquid crystal panel is not included.
18. The liquid crystal display of claim 17, wherein the backlight
unit further includes a light guide between the prism sheet and the
reflection sheet, and the light source is disposed at a side of the
light guide.
19. The liquid crystal display of claim 17, wherein the liquid
crystal panel further includes a diffuser attached to an upper
surface of the upper polarizer.
20. The liquid crystal display of claim 19, wherein the diffuser
diffuses the light incident thereto to the short side direction of
the liquid crystal panel.
Description
[0001] This application claims priority to Korean Patent
Application No. 10-2018-0108355, filed on Sep. 11, 2018, and all
the benefits accruing therefrom under 35 U.S.C. .sctn. 119, the
content of which in its entirety is herein incorporated by
reference.
BACKGROUND
(a) Field
[0002] The disclosure relates to a liquid crystal display, and in
detail, relates to a high-resolution liquid crystal display having
high transmittance.
(b) Description of the Related Art
[0003] A liquid crystal display may include two field generating
electrodes, a liquid crystal layer, a color filter, and a
polarization layer. Light generated from a light source reaches a
viewer after passing through the liquid crystal layer, the color
filter and the polarization layer, and a polarization
characteristic of light is changed depending on an arrangement
angle of the liquid crystal layer, and as a result, a grayscale of
an image displayed by the light from the light source is controlled
while light is partially blocked by the polarization layer.
SUMMARY
[0004] When the resolution of a display device becomes higher, a
size of the pixel becomes smaller such that the transmittance
decreases when the display device is displayed in a conventional
method.
[0005] Exemplary embodiments are directed to a liquid crystal
display having high transmittance.
[0006] An exemplary embodiment of a liquid crystal display
includes: a liquid crystal panel including a liquid crystal layer,
a pixel electrode, and a common electrode; and a backlight unit
including a light source, where the backlight unit provides light
to the liquid crystal panel. In such an embodiment, the pixel
electrode includes: a longitudinal electrode having a bar shape and
extending in a vertical direction; a transverse electrode having a
bar shape, crossing the longitudinal electrode, and extending in a
horizontal direction; and a branch electrode having a bar shape,
extending from the longitudinal electrode and the transverse
electrode, and including an oblique part extending in an oblique
direction with respect to the longitudinal electrode or the
transverse electrode. In such an embodiment, the common electrode
has a longitudinal opening overlaping the longitudinal electrode of
the pixel electrode, and extending in the vertical direction, and a
width of a part of the pixel electrode where the longitudinal
electrode and the transverse electrode cross each other is
substantially the same as a width of the transverse electrode or a
width of the longitudinal electrode.
[0007] In an exemplary embodiment, the pixel electrode may further
include an edge transverse electrode having a bar shape, extending
in the horizontal direction, and connected to an end of the
longitudinal electrode.
[0008] In an exemplary embodiment, the edge transverse electrode
may be connected to an end of the branch electrode.
[0009] In an exemplary embodiment, the oblique part of the branch
electrode may form an angle in a range of about 60 degrees to about
80 degrees with the transverse electrode.
[0010] In an exemplary embodiment, the common electrode may further
includes a notch opening having a width extended at the
longitudinal opening.
[0011] In an exemplary embodiment, the notch opening may overlap
the part where the longitudinal electrode and the transverse
electrode cross each other.
[0012] In an exemplary embodiment, the pixel electrode may further
include an edge longitudinal electrode having a bar shape,
connected to an end of the transverse electrode, and parallel to
the longitudinal electrode.
[0013] In an exemplary embodiment, the pixel electrode may further
include an edge longitudinal electrode having a bar shape and
parallel to the longitudinal electrode, and the edge longitudinal
electrode may be connected to an end of the branch electrode and
may not be connected to the transverse electrode.
[0014] In an exemplary embodiment, the branch electrode may further
include a part parallel to the transverse electrode or the
longitudinal electrode, thereby defining a bent structure with the
oblique part.
[0015] In an exemplary embodiment, the common electrode may further
includes a notch opening having a width extended at the
longitudinal opening, and the notch opening may overlap the part
where the longitudinal electrode and the transverse electrode cross
each other.
[0016] In an exemplary embodiment, the notch opening may extend to
be parallel to the transverse electrode.
[0017] In an exemplary embodiment, the pixel electrode may include
a first pixel electrode and a second pixel electrode adjacent to
each other, the liquid crystal panel may further include a first
gate line, a second gate line, a first data line, a second data
line, a first thin film transistor, and a second thin film
transistor, the first thin film transistor may be connected to the
first pixel electrode and connected to the first gate line and the
first data line, and the second thin film transistor may be
connected to the second pixel electrode and connected to the second
gate line and the second data line.
[0018] In an exemplary embodiment, the first gate line and the
second gate line may receive a same gate signal as each other.
[0019] In an exemplary embodiment, the first pixel electrode and
the second pixel electrode may be arranged along an extending
direction of the first data line and the second data line, and the
first data line and the second data line may be disposed to cross
the first pixel electrode and the second pixel electrode,
respectively.
[0020] In an exemplary embodiment, the liquid crystal panel may
further include an upper polarizer and a lower polarizer attached
at both sides thereof, respectively.
[0021] In an exemplary embodiment, the backlight unit may further
include a prism sheet disposed under the liquid crystal panel and a
reflection sheet disposed under the prism sheet, the prism sheet
may have a prism hill, and the prism hill may be disposed toward
the reflection sheet.
[0022] In an exemplary embodiment, an extending direction of the
prism hill may be the same as a short side direction of the liquid
crystal panel, and a prism hill extending in a long side direction
of the liquid crystal panel may not be included.
[0023] In an exemplary embodiment, the backlight unit may further
include a light guide between the prism sheet and the reflection
sheet, and the light source may be disposed at a side of the light
guide.
[0024] In an exemplary embodiment, the liquid crystal panel may
further include a diffuser attached to an upper surface of the
upper polarizer.
[0025] In an exemplary embodiment, the diffuser may diffuse the
light incident thereto to the short side direction of the liquid
crystal panel.
[0026] According to exemplary embodiments, even if a size of the
pixel decreases as the liquid crystal display having high
resolution, the arrangement direction of the liquid crystal
molecules is arranged to have high transmittance, thereby obtains
high transmittance. In such embodiments, the characteristic
deterioration from a side view due to the arrangement
characteristic of the liquid crystal molecules is effectively
compensated by using the reversely-arranged prism sheet that
transmits the light in the left and right side directions.
[0027] In such embodiments, a writing time of the data voltage is
effectively secured in a case of high resolution. In such
embodiments, two data lines may be disposed for one pixel column,
such that the pixels of two rows may be turned on with the same
timing. In such embodiments, two data lines may be disposed to
cross the pixel, such that a region covered by a black matrix is
reduced, thereby improving transmittance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The above and other features of the invention will become
more apparent by describing in further detail exemplary embodiments
thereof with reference to the accompanying drawings, in which:
[0029] FIG. 1 is a schematic view showing a connection relationship
of a pixel electrode in a liquid crystal display according to an
exemplary embodiment;
[0030] FIG. 2 is a cross-sectional view showing an entire structure
of a liquid crystal display according to an exemplary
embodiment;
[0031] FIG. 3 is a top plan view showing a structure of a pixel
electrode and a common electrode in a pixel according to an
exemplary embodiment;
[0032] FIG. 4 is a view showing an arrangement of liquid crystal
molecules according to an electrode structure of FIG. 3;
[0033] FIG. 5 is a view showing an arrangement of liquid crystal
molecules depending on an angle of a branch electrode in a pixel
electrode according to an exemplary embodiment;
[0034] FIG. 6 is a view showing transmittance depending on an angle
of a branch electrode in a pixel electrode according to an
exemplary embodiment;
[0035] FIG. 7 is a view of a structure of a pixel electrode, an
arrangement of liquid crystal molecules, and transmittance
according to an exemplary embodiment;
[0036] FIG. 8 is a view showing transmittance according to a
comparative example and an exemplary embodiment;
[0037] FIG. 9 is a view showing an arrangement of liquid crystal
molecules according to a comparative example and an exemplary
embodiment;
[0038] FIG. 10 is a view showing a characteristic change depending
on a change of a notch in a common electrode according to an
exemplary embodiment;
[0039] FIG. 11 is a view showing a luminance change in a front and
a side according to a comparative example and an exemplary
embodiment;
[0040] FIG. 12 is a view showing an arrangement characteristic of a
liquid crystal molecule depending on a voltage at a specific
position in a comparative example and an exemplary embodiment;
[0041] FIG. 13 is a view showing an angle depending on a position
of a liquid crystal molecule depending on a voltage in a
comparative example and an exemplary embodiment;
[0042] FIG. 14 is a view showing a structure of a pixel electrode
and a common electrode according to various exemplary
embodiments;
[0043] FIG. 15 is a view showing a structure of a common electrode
according to various exemplary embodiments;
[0044] FIG. 16 is a view showing light leakage in an upper side for
an arrangement of liquid crystal molecules according to an
exemplary embodiment;
[0045] FIG. 17 is a view showing a characteristic depending on a
position for an arrangement of a liquid crystal molecule according
to an exemplary embodiment;
[0046] FIG. 18 is a view showing a characteristic of light provided
from a backlight unit of a liquid crystal display according to an
exemplary embodiment;
[0047] FIG. 19 is a view showing characteristic of a prism sheet
according to a comparative example and characteristics of a prism
sheet according to an exemplary embodiment;
[0048] FIG. 20 is a view showing a characteristic that is changed
by using a prism sheet according to an exemplary embodiment;
and
[0049] FIG. 21 is a view showing a characteristic of light per each
position of a liquid crystal display according to an exemplary
embodiment.
DETAILED DESCRIPTION
[0050] The invention will be described more fully hereinafter with
reference to the accompanying drawings, in which exemplary
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms, and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like reference numerals
refer to like elements throughout.
[0051] Further, in the drawings, a size and thickness of each
element are arbitrarily represented for better understanding and
ease of description, and the invention is not limited thereto. In
the drawings, the thickness of layers, films, panels, regions,
etc., are exaggerated for clarity. In the drawings, the thickness
of layers, films, panels, regions, etc., are exaggerated for the
convenience of description.
[0052] It will be understood that when an element such as a layer,
film, region, or substrate is referred to as being "on" another
element, it can be directly on the other element or intervening
elements may also be present. In contrast, when an element is
referred to as being "directly on" another element, there are no
intervening elements present. Further, in the specification, the
word "on" or "above" means positioned on or below the object
portion, and does not necessarily mean positioned on the upper side
of the object portion based on a gravitational direction.
[0053] It will be understood that, although the terms "first,"
"second," "third" etc. may be used herein to describe various
elements, components, regions, layers and/or sections, these
elements, components, regions, layers and/or sections should not be
limited by these terms. These terms are only used to distinguish
one element, component, region, layer or section from another
element, component, region, layer or section. Thus, "a first
element," "component," "region," "layer" or "section" discussed
below could be termed a second element, component, region, layer or
section without departing from the teachings herein.
[0054] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting. As
used herein, the singular forms "a," "an," and "the" are intended
to include the plural forms, including "at least one," unless the
content clearly indicates otherwise. "Or" means "and/or." "at least
one of A and B" means "A and/or B." As used herein, the term
"and/or" includes any and all combinations of one or more of the
associated listed items. It will be further understood that the
terms "comprises" and/or "comprising," or "includes" and/or
"including" when used in this specification, specify the presence
of stated features, regions, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, regions, integers, steps, operations,
elements, components, and/or groups thereof.
[0055] The phrase "on a plane" means viewing the object portion
from the top, and the phrase "on a cross-section" means viewing a
cross-section of which the object portion is vertically cut from
the side.
[0056] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" other elements or features would
then be oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly.
[0057] "About" or "approximately" as used herein is inclusive of
the stated value and means within an acceptable range of deviation
for the particular value as determined by one of ordinary skill in
the art, considering the measurement in question and the error
associated with measurement of the particular quantity (i.e., the
limitations of the measurement system).
[0058] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0059] Exemplary embodiments are described herein with reference to
cross section illustrations that are schematic illustrations of
idealized embodiments. As such, variations from the shapes of the
illustrations as a result, for example, of manufacturing techniques
and/or tolerances, are to be expected. Thus, embodiments described
herein should not be construed as limited to the particular shapes
of regions as illustrated herein but are to include deviations in
shapes that result, for example, from manufacturing. For example, a
region illustrated or described as flat may, typically, have rough
and/or nonlinear features. Moreover, sharp angles that are
illustrated may be rounded. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the precise shape of a region and are not intended to
limit the scope of the present claims.
[0060] Hereinafter, exemplary embodiments of the invention will be
described in detail with reference to the accompanying
drawings.
[0061] FIG. 1 is a schematic view showing a connection relationship
of a pixel electrode in a liquid crystal display according to an
exemplary embodiment.
[0062] A relationship of a pixel electrode 190, gate lines Gi,
G(i-1), and G(i-2), data lines Dj, D'j, D(j+1), and D'(j+1), and a
thin film transistor TFT in a lower panel of the liquid crystal
display according to an exemplary embodiment will be described in
detail with reference to FIG. 1.
[0063] In an exemplary embodiment, the lower panel of the liquid
crystal display has a structure in which one gate line Gi is
divided into two gate lines G(i-1) and G(i-2) to be connected to
pixel electrodes 190 of two rows. In such an embodiment, two data
lines (a pair of data lines) are disposed in a column of pixel
electrodes 190. In an exemplary embodiment, as shown in FIG. 1, two
data lines Dj and D'j are disposed to vertically extend and cross a
pixel electrode 190 of the pixel electrodes 190 of a first column,
e.g., a left column, and other two data lines D(j+1) and D'(j+1)
are disposed to vertically extend and cross a pixel electrode 190
of the pixel electrodes 190 of a second column, e.g., a right
column. Here, a vertical direction may be an extending direction of
the data line, and a horizontal direction may be direction
perpendicular to the vertical direction when viewed from a plane
view in a thickness direction of the lower panel of the liquid
crystal display.
[0064] Two thin film transistors TFT, which are connected to the
pixel electrodes 190 included in one column of pixel electrode 190s
and vertically adjacent to each other, are connected to the gate
lines G(i-1) and G(i-2) that are different from each other and the
data lines Dj, D(j+1) and D'(j+1) that are different from each
other. In such an embodiment, the gate lines G(i-1) and G(i-2) that
are different from each other may be connected to each other, that
is, the ends thereof are connected to one gate line Gi such that a
same gate-on voltage is simultaneously applied thereto. The data
lines Dj, D'j, D(j+1) and D'(j+1) are not connected to each other
such that data voltages that are different from each other may be
applied to the two thin film transistors TFT vertically adjacent to
each other.
[0065] The connection relationship of four adjacent pixel
electrodes 190, the thin film transistors TFT, the gate lines
G(i-1) and G(i-2), and the data lines Dj, D'j, D(j+1), and D'(j+1)
will be described in detail with reference to FIG. 1.
[0066] FIG. 1 shows four pixel electrodes 190 adjacent vertically
and horizontally. Each pixel electrode 190 is connected a
corresponding thin film transistor TFT, that is, an output terminal
thereof.
[0067] Among the thin film transistors TFT connected to the gate
lines G(i-1) and G(i-2), the thin film transistors TFT disposed on
a same row are connected to a same gate line, and the thin film
transistors TFT disposed on different rows are connected to
different gate lines. Each of the gate lines G(i-1) and G(i-2) is
disposed between the pixel electrodes, and side ends of two gate
lines G(i-1) and G(i-2) are merged into a single gate line Gi,
thereby receiving a same gate signal. When the gate lines receiving
a same gate signal are referred to as one gate line, the number of
the gate lines may be half of that of the rows of the pixel
electrodes 190. On the other hand, the number of all gate lines
extending horizontally is the same as the number of the rows of the
pixel electrodes 190.
[0068] Input terminals of the thin film transistors TFT are
connected to the data lines Dj, D'j, D(j+1), and D'(j+1), and the
thin film transistors TFT vertically adjacent to each other may be
connected to different data lines. In an exemplary embodiment, when
the gate signal applied to the thin film transistors TFT is the
same as each other, the thin film transistors TFT are connected to
different data lines, respectively. In an exemplary embodiment, as
shown in FIG. 1, the thin film transistor TFT disposed at the
left-upper side is connected to the data line Dj disposed at the
left side among a pair of data lines Dj and D'j, and the thin film
transistor TFT disposed at the left-lower side is connected to the
data line D'j disposed at the right side. In an exemplary
embodiment, as shown in FIG. 1, the thin film transistor TFT
disposed at the right-upper side is connected to the data line
D(j+1) disposed at the left side, and the thin film transistor TFT
disposed at the right-lower side is connected to the data line
D'(j+1) disposed at the right side. In an alternative exemplary
embodiment, the thin film transistor TFT disposed at the
right-upper side may be connected to the data line D'(j+1) disposed
at the right side, and the thin film transistor TFT disposed at the
right-lower side may be connected to the data line D(j+1) disposed
at the left side.
[0069] In an exemplary embodiment, a pair of data lines is disposed
to extend vertically along the pixel electrode 190. In such an
embodiment, if the pixel electrode 190 is divided into the left
region and the right region based on the center of the pixel
electrode 190, the pair of data lines may be disposed at the left
region and the right region of the pixel electrode 190,
respectively. In such an embodiment, the data line may be disposed
while crossing a normal center of the left region or the right
region. In an exemplary embodiment, as above-described, the data
lines Dj, D'j, D(j+1), and D'(j+1) overlap the pixel electrode 190,
such that the interval between the pixel electrodes 190 adjacent to
each other in the horizontal direction may be reduced, thereby
reducing an area covered by a black matrix BM. As a result, in such
an embodiment, a transmittance is improved.
[0070] In an exemplary embodiment, the thin film transistor TFT,
the gate lines Gi, G(i-1), and G(i-2), and the data lines Dj, D'j,
D(j+1), and D'(j+1) in the display panel may be connected as
described above.
[0071] Such a structure of FIG. 1 may be disposed in the lower
panel among liquid crystal panels constituting the liquid crystal
display. The liquid crystal panel includes the lower panel and an
upper panel, and a liquid crystal layer interposed between the
lower and upper panels. In an exemplary embodiment, the liquid
crystal display further includes a backlight unit.
[0072] The structure of the liquid crystal display will be
described with reference to FIG. 2.
[0073] FIG. 2 is a cross-sectional view showing an entire structure
of a liquid crystal display according to an exemplary
embodiment.
[0074] In an exemplary embodiment, as shown in FIG. 2, the liquid
crystal display includes the liquid crystal panel (100, 310, 320
and 330) and the backlight unit (400, 410, 420 and 430).
[0075] The liquid crystal panel includes a display panel 100, a
lower polarizer 310, an upper polarizer 320, and a diffusion layer
330.
[0076] In an exemplary embodiment, although not shown in FIG. 2,
the display panel 100 includes the upper panel and the lower panel,
and the liquid crystal layer interposed therebetween. In such an
embodiment, as described above with reference to FIG. 1, the pixel
electrode 190, the gate line, the data line, and the thin film
transistor TFT are disposed in the lower panel. In such an
embodiment, a common electrode 270 (shown in FIG. 3) is disposed in
the upper panel, and an opening is defined in the common electrode
270. An arrangement direction of the liquid crystal molecules
included in the liquid crystal layer is changed depending on an
electric field generated by the pixel electrode 190 and the common
electrode 270. In an exemplary embodiment, the liquid crystal
molecules are a liquid crystal of a vertically aligned ("VA") mode
in which the liquid crystal molecules are aligned vertically, e.g.,
in a perpendicular direction with respect to the upper or lower
panel, in the absence of the electric field.
[0077] The lower polarizer 310 and the upper polarizer 320 are
disposed, e.g., attached, on both surfaces of the display panel
100. Since each of the two polarizers 310 and 320 have a
transmissive axis, light having a polarization characteristic
parallel to the transmissive axis is transmitted and light having
the polarization characteristic of the direction perpendicular to
the transmissive axis is blocked. The transmissive axes of the two
polarizers 310 and 320 may be perpendicular to each other.
[0078] The diffusion layer 330 is disposed on the upper polarizer
320. In an exemplary embodiment, the diffusion layer 330 has a
characteristic of diffusing light in one direction. Here, the one
direction may be the direction parallel to the short side direction
of the liquid crystal panel, and the short side direction of the
liquid crystal panel may be the same as the extending direction of
the data line. That is, the diffusion layer 330 diffuses light
emitted toward the front surface of the liquid crystal panel to the
short side direction of the liquid crystal panel, thereby obtaining
an effect of increasing the luminance when viewing in the upper
side or lower side of the front surface of the liquid crystal
panel.
[0079] In an exemplary embodiment, the backlight unit of the liquid
crystal display includes a light source 410, a light guide 400, a
reflection sheet 430, and a prism sheet 420.
[0080] The light source 410 includes a light emitting diode
("LED"), etc., and may emit light to be provided to the liquid
crystal panel.
[0081] In an exemplary embodiment, as shown in FIG. 2, light
emitted from the light source 410 is incident to the side surface
of the light guide 400. The light guide 400 transmits the light to
an end thereof where the light source 410 is not provided, and the
reflection sheet 430 is configured in a way such that the light is
not emitted downward. The light incident to the reflection sheet
430 is reflected back to the light guide 400. The light passing
through the light guide 400 and the reflection sheet 430 is
incident to the prism sheet 420 disposed thereon.
[0082] The prism sheet 420 includes a plurality of prism structure
members arranged in parallel to each other, and each prism
structure member has a cross-section of a triangle and includes a
prism hill extending long in one direction. One corner of the
triangular cross-sectionals of the prism structure member forms the
prism hill. The prism hill protrudes toward the rear surface of the
liquid crystal display. In such an embodiment, the prism hill is
positioned toward the light guide 400 or the reflection sheet 430.
In such an embodiment, the prism structure member is disposed at
the lower surface of the prism sheet 420, and the upper surface of
the prism sheet 420 toward the liquid crystal panel has a flat
structure.
[0083] In an exemplary embodiment, the backlight unit may include a
single prism sheet 420. In such an embodiment, the extending
direction of the prism hill is only one direction. In such an
embodiment, the extending direction of the prism hill is the short
side direction of the liquid crystal panel. The short side
direction of the liquid crystal panel is the same as the extending
direction of the data line and the length direction of the pixel
electrode 190.
[0084] FIG. 2 shows the cross-sectional structure of the triangle
taken along the direction perpendicular to the extending direction
of the prism hill of the prism sheet 420.
[0085] In such an embodiment, since the prism sheet 420 is defined
by a single sheet, a prism sheet matching the long side direction
of the liquid crystal panel or having a prism hill extending in a
same direction as the gate line is not provided.
[0086] Such a prism sheet 420 has the prism hill extending in the
short side direction (the direction of the data line) of the liquid
crystal panel, thereby the light is refracted and progresses in the
direction perpendicular thereto. In such an embodiment, the light
incident to the prism sheet 420 is refracted from the prism
surface, which is obliquely formed, to both sides based on the
prism hill and progresses in the left/right side directions. As a
result, the light progressing in the direction (the long side
direction of the liquid crystal panel or the direction of the gate
line) perpendicular to the short side direction (the direction of
the data line) of the liquid crystal panel is further increased.
(Referring to FIG. 18)
[0087] In an exemplary embodiment, as above described, where a
single prism sheet 420 is used, the light progressing in the long
side direction of the liquid crystal panel is increased such that
the light progressing in the short side direction of the liquid
crystal panel may be relatively decreased. In such an embodiment,
the display panel 100 includes the diffusion layer 330 having the
characteristic of diffusing the light in the short side direction
of the liquid crystal panel on the display panel 100 to compensate
the decrease of the light progressing in the short side direction
of the liquid crystal panel, such that the light may be entirely
and uniformly transmitted. (Referring to FIG. 21)
[0088] The path through which the light passes will hereinafter be
described with reference to FIG. 2.
[0089] The light emitted from the light source 410 is transmitted
through the light guide 400, and the reflection sheet 430 disposed
at the lower surface of the light guide 400 transmits the light
emitted below the light guide 400 to the prism sheet 420 or an
upper side. The light enters the lower polarizer 310 of the display
panel 100, while the light further includes the component of the
light transmitted to the left and right directions (the long side
direction of the liquid crystal panel) when the light passes
through the prism sheet 420. Only the light having the same
polarization characteristic as the transmissive axis of the lower
polarizer 310 is transmitted and enters the display panel 100. The
phase retardation of the light changes while passing through the
liquid crystal layer of the display panel 100 such that the
polarization characteristic may be changed of the light, and the
transmission degree for the upper polarizer 320 is changed
according to the changed polarization characteristic of the light.
The light passing through the upper polarizer 320 is diffused in
the up and down directions (the short side direction of the liquid
crystal panel) while passing through the diffusion layer 330, and
displays the image with light, the characteristic of which changed
by the prism sheet 420 is compensated.
[0090] FIG. 2 shows an exemplary embodiment in which the light
source 410 is disposed at a side surface of the light guide 400.
However, the invention is not limited thereto. According to an
alternative exemplary embodiment, the backlight may have a
direct-type structure, in which a hole is defined in the reflection
sheet 430 and a light source is disposed in the corresponding hole.
In such an embodiment, a lens may be disposed on the light source
and the light guide may be omitted.
[0091] Next, the pattern of the pixel electrode and the common
electrode among the structure of the display panel 100 will be
described with reference to FIG. 3.
[0092] FIG. 3 is a top plan view showing a structure of a pixel
electrode and a common electrode in a pixel according to an
exemplary embodiment.
[0093] FIG. 3 (A) shows a structure of a part of the common
electrode 270 corresponding to the pixel electrode 190 according to
an exemplary embodiment. Referring to FIG. 3 (A), a longitudinal
opening 271 and a notch opening 275 are defined in the common
electrode 270 disposed in the upper panel. The longitudinal opening
271 extends in a same direction as the extending direction of the
data line. Also, one notch opening 275 may be defined for every
pixel electrode 190, and may be disposed at the position
corresponding to the predetermined position of the pixel electrode
190 among the longitudinal opening 271. Common electrodes 270 are
formed to be connected to each other between the adjacent pixel
electrodes 190.
[0094] In an exemplary embodiment, the notch opening 275 may have
one of various shapes, e.g., a shape extending in the direction
perpendicular to the longitudinal opening 271. Alternatively, the
notch opening 275 may be omitted.
[0095] In an exemplary embodiment, a protrusion structure may be
provided in the common electrode 270 instead of the openings 271
and 275. The protrusion structure may be provided by forming an
additional protrusion pattern on the common electrode 270.
[0096] FIG. 3 (B) shows the structure of a pixel electrode 190
according to an exemplary embodiment. Referring to FIG. 3 (B), the
pixel electrode 190 includes a longitudinal electrode 191 having a
bar shape, a transverse electrode 192 having a bar shape, and a
branch electrode 193 extending from the longitudinal electrode 191
or the transverse electrode 192 in an oblique direction. The branch
electrode 193 forms a predetermined angle .alpha. with the
transverse electrode 192. FIG. 3 (B) shows an exemplary embodiment
in which the branch electrode 193 forms an angle of about
45.degree. with the transverse electrode 192. However, the
invention is not limited thereto. According to an alternative
exemplary embodiment, an angle exceeding 45.degree. may be formed.
In an exemplary embodiment, the pixel electrode 190 is divided into
four domains by the longitudinal electrode 191 and the transverse
electrode 192, and the branch electrodes 193 included in one domain
may extend in a direction parallel to each other and may be
arranged with a predetermined interval.
[0097] FIG. 3 (C) shows a structure in which the pixel electrode
190 and the common electrode 270 are disposed to overlap each
other. When the upper panel including the common electrode 270 and
the lower panel including the pixel electrode 190 are assembled,
the pixel electrode 190 and the common electrode 270 are aligned to
overlap each other as shown in FIG. 3 (C).
[0098] As shown in FIG. 3 (C), the longitudinal electrode 191 of
the pixel electrode 190 overlaps the longitudinal opening 271 of
the common electrode 270. In such an embodiment, the notch opening
275 of the common electrode 270 is defined to overlap a part where
the longitudinal electrode 191 and the transverse electrode 192
cross each other. In an exemplary embodiment, the part of the pixel
electrode 190 where the longitudinal electrode 191 and the
transverse electrode 192 cross each other has a width substantially
the same as a width of the longitudinal electrode 191 or a width of
the transverse electrode 192 such that the part is not expanded
from the longitudinal electrode 191 and the transverse electrode
192.
[0099] Next, an arrangement direction of the liquid crystal
molecule for the electrode structure of FIG. 3 will be described
with reference to FIG. 4.
[0100] FIG. 4 is a view showing an arrangement of liquid crystal
molecules according to an electrode structure of FIG. 3.
[0101] Hereinafter, the angle .PHI. will be used to describe the
arrangement of the liquid crystal molecules, and the angle .PHI. is
defined as follows.
[0102] The angle .PHI. of the liquid crystal molecule means the
angle of the long axis of the liquid crystal molecule 305 with the
transverse electrode 192 of the pixel electrode 190 after
projecting the long axis direction of the liquid crystal molecule
305 having a three-dimensional structure to the surface of the
pixel electrode 190 parallel to the substrate surface of the
display panel 100. The direction of the transverse electrode 192 is
the same as the extending direction of the gate line, that is, a
direction perpendicular to the direction of the longitudinal
opening 271 and the longitudinal electrode 191.
[0103] FIG. 4 (A) shows the shape of the liquid crystal molecules
305 arranged adjacent to the common electrode 270.
[0104] Referring to FIG. 4 (A), the liquid crystal molecule 305
adjacent to the common electrode 270 is arranged along one side
edge of the longitudinal opening 271, and the long axis direction
of the liquid crystal molecule 305 is aligned in a direction (i.e.,
the extending direction of the gate line) perpendicular to the
longitudinal opening 271. As a result, the angle .PHI. of the
liquid crystal molecule 305 is about 0.degree.. In such an
embodiment, the liquid crystal molecule 305 arranged near the edge
of the notch opening 275 is arranged in the different direction
from the liquid crystal molecule 305 along the longitudinal opening
271. The long axis direction of the liquid crystal molecule 305 is
entirely aligned in the direction (the angle .PHI. is about
0.degree.) perpendicular to the longitudinal opening 271 except for
the liquid crystal molecule 305 near the notch opening 275.
[0105] FIG. 4 (B) shows the shape of the liquid crystal molecule
305 arranged adjacent to the pixel electrode 190.
[0106] Referring to FIG. 4 (B), the angle .PHI. of the liquid
crystal molecule 305 disposed near the longitudinal electrode 191
of the pixel electrode 190 is about 90.degree. with respect to the
transverse electrode 192. In such an embodiment, the liquid crystal
molecule 305 is arranged to be substantially parallel to the
transverse electrode 192 on the right and left edges of the pixel
electrode 190, such that the angle .PHI. is almost 0.degree.. The
arrangement of the liquid crystal molecules 305 between the
longitudinal electrode 191 and the left and right edges
(hereinafter referred to as `a middle part`) forms a middle angle
of two angle .PHI. on the part where the longitudinal electrode 191
is disposed and the part (hereinafter referred to as `a middle
part`) at the left and right edges such that the angle .PHI. of the
liquid crystal molecule 305 between the longitudinal electrode 191
and the left and right edges is about 45.degree..
[0107] FIG. 4 (A) shows a part of the liquid crystal molecules 305
close to the upper panel in the liquid crystal layer because the
liquid crystal molecule 305 is close to the common electrode 270,
and FIG. 4 (B) shows a part of the liquid crystal molecules 305
close to the lower panel in the liquid crystal layer because the
liquid crystal molecule 305 is close to the pixel electrode
190.
[0108] Since the liquid crystal layer is disposed between the upper
panel and the lower panel, the angle .PHI. of the liquid crystal
molecule disposed between those shown in FIGS. 4 (A) and (B), that
is, the angle .PHI. for the liquid crystal molecule of the middle
layer departed from and upper panel and the lower panel by a
predetermined distance, will be described with reference to FIG. 4
(C).
[0109] The liquid crystal molecule 305 of the middle layer has a
middle angle .PHI. between the angle .PHI. of the liquid crystal
molecule 305 of FIG. 4 (A) and FIG. 4 (B), as shown in FIG. 4 (C).
In such an embodiment, since the angles .PHI. of 0.degree. and
90.degree. are formed on the parts corresponding to the
longitudinal electrode 191 and the longitudinal opening 271, the
liquid crystal molecule 305 of the middle layer may have an angle
of 45.degree. as the middle angle therebetween. The liquid crystal
molecule 305 of the middle layer corresponding to the left and
right edge of the pixel electrode 190 has an angle of about 0
because the angle is 0.degree. near the common electrode 270 and
the angle near the pixel electrode 190 is almost 0.degree..
[0110] In such an embodiment, the liquid crystal molecules 305
corresponding to the middle layer of the middle part are affected
by the angle of all adjacent liquid crystal molecules. As a result,
the middle angle between 0.degree. and 45.degree. is formed.
[0111] Accordingly, as described above, the liquid crystal molecule
disposed at the middle layer of the middle part may be arranged
with an angle of 45.degree. or less.
[0112] In an exemplary embodiment, the transmittance has a maximum
value when the angle .PHI. of the liquid crystal molecule 305 is
45.degree., and it has a minimum value in the case of 0.degree. or
90.degree.. Therefore, to improve the transmittance, it is desired
to increase the angle .PHI. of the liquid crystal molecule in the
middle layer of the middle part to be about 45.degree., as will be
described with reference to FIG. 5.
[0113] FIG. 5 is a view showing an arrangement of a liquid crystal
molecule depending on an angle of a branch electrode in a pixel
electrode according to an exemplary embodiment.
[0114] In FIG. 5, an exemplary embodiment in which the angle
.alpha. between the branch electrode 193 and the transverse
electrode 192 is 45.degree. is shown at the left side, and an
exemplary embodiment in which the angle .alpha. is 60.degree. or
more is shown at the right side. Also, FIG. 5 shows the angle .PHI.
of the liquid crystal molecule in the middle layer.
[0115] First, as shown in FIGS. 4 and 5, the angle .alpha. between
the branch electrode 193 and the transverse electrode 192 is about
45.degree., and the angle .PHI. of the liquid crystal molecule 305
may be less than about 45.degree. in the middle layer of the middle
part.
[0116] In an exemplary embodiment, as shown in the right side of
FIG. 5, when the angle .alpha. of the branch electrode 193 is about
60.degree. or more, the angle .PHI. of the liquid crystal molecule
305 disposed at the middle layer of the middle part may be about
45.degree..
[0117] As a result, in such an embodiment, the transmittance is
increased. The change of the transmittance according to the angle
.alpha. of the branch electrode 193 will hereinafter described with
reference to FIG. 6.
[0118] FIG. 6 is a view showing transmittance depending on an angle
of a branch electrode in a pixel electrode according to an
exemplary embodiment.
[0119] FIG. 6 shows the transmittance according to a comparative
example (Reference SVA) and the transmittance change according to
the angle .alpha. of the branch electrode 193.
[0120] First, the comparative example (Reference SVA) has a
structure in which the pattern of the pixel electrode 190 is the
same as an exemplary embodiment described above, but the opening is
not separately formed in the common electrode 270, and the change
of the transmittance in exemplary embodiments is shown in FIG. 6
when the transmittance of the comparative example (Reference SVA)
is considered as 100.
[0121] A black line in the view showing a transmission degree in
FIG. 6 represents the data line, the gate line, the storage
electrode, etc. In FIG. 6, two lines vertically crossing the center
of the pixel electrode correspond to the data lines, the horizontal
lines disposed above and below the pixel electrode correspond to
the gate lines, and the line disposed near both edges of the pixel
electrode correspond to the storage electrode.
[0122] In FIG. 6, when the angle .alpha. of the branch electrode
193 is about 45.degree., the transmittance is improved as 106%
compared with the comparative example. It may be shown that the
black color is reduced at the longitudinal electrode 191 part of
the pixel electrode 190 due to the longitudinal opening 271 formed
in the common electrode 270, and as a result, the transmittance is
improved.
[0123] In FIG. 6, when the angle .alpha. of the branch electrode
193 is about 55.degree., it may be shown that the transmittance is
improved as 118%. While the angle .alpha. of the branch electrode
193 is increased and then the angle of the liquid crystal molecule
disposed at the corresponding part is increased to be close to
45.degree., the transmittance is improved.
[0124] The views at the right side of FIG. 6 show two exemplary
embodiments where the angle .alpha. of the branch electrode 193 is
about 65.degree.. The second view from the right side shows an
exemplary embodiment where the angle .alpha. of the branch
electrode 193 is 65.degree., and the pixel electrode 190 has the
longitudinal electrode 191, the transverse electrode 192 and the
branch electrode 193 as shown in FIG. 3 (B).
[0125] The view at the rightmost side shows an exemplary embodiment
where the edge transverse electrode is disposed above and below the
pixel electrode 190 as shown in FIG. 7.
[0126] In such an embodiment, referring to FIG. 6, when the angle
.alpha. of the branch electrode 193 is 65.degree. and the edge
transverse electrode is additionally formed in the pixel electrode
190, the highest transmittance may be obtained as the transmittance
of 125%. That is, comparing the drawing of the rightmost side and
the drawing of the second right side in FIG. 6, it may be shown
that the black degree is differentiated at the part adjacent to the
edge transverse electrode. That is, the transmittance of the
corresponding part is improved due to the edge transverse electrode
such that the transmittance is improved from 123% to 125%.
[0127] Next, the rightmost structure of FIG. 6 will be described in
detail with reference to FIG. 7.
[0128] FIG. 7 is a view of a structure of a pixel electrode, an
arrangement of liquid crystal molecules, and transmittance
according to an exemplary embodiment.
[0129] First, the structure of the pixel electrode 190 will be
described.
[0130] According to an exemplary embodiment, as shown in FIG. 7,
one pixel electrode 190 includes the longitudinal electrode 191,
the transverse electrode 192, the branch electrode 193 and the edge
transverse electrode 196 connecting the branch electrode 193 and
the longitudinal electrode 191. The edge transverse electrode 196
may be parallel to the transverse electrode 192. The branch
electrode 193 forms an angle .alpha. of about 65.degree. with the
transverse electrode 192. The edge transverse electrode 196
connects upper ends of the branch electrodes 193, so that the upper
ends of the branch electrodes 193 are not opened. In such an
embodiment, four domains defined by the longitudinal electrode 191
and the transverse electrode 192 have the structure that is opened
on the left and right edges and is closed on the upper and lower
edges.
[0131] The common electrode 270 has the same structure as that of
FIG. 3 (A). In such an embodiment, the common electrode 270
includes the longitudinal opening 271 and the notch opening 275,
the longitudinal opening 271 is disposed at the position
overlapping the longitudinal electrode 191, while the notch opening
275 is formed to overlap the position where the longitudinal
electrode 191 and the transverse electrode 192 cross each
other.
[0132] In such an embodiment, as described above, the angle .PHI.
of the liquid crystal molecules 305 disposed at various positions
is about 45.degree.. Therefore, the transmittance is substantially
high.
[0133] Referring to FIG. 7, if the branch electrode 193 has an
angle in a range of about 60 degrees to about 80 degrees with the
transverse electrode 192 the angle .PHI. of the liquid crystal
molecule 305 corresponding thereto is about 45.degree. such that
the transmittance is improved.
[0134] Next, a difference of transmittance according to the
comparative example and an exemplary embodiment will be described
with reference to FIG. 8.
[0135] FIG. 8 is a view showing transmittance according to a
comparative example and an exemplary embodiment.
[0136] First, the comparative example on the left side has a
structure in which the opening is not formed in the common
electrode 270, and the exemplary embodiment on the right side has a
structure shown in FIG. 7.
[0137] The transmittance at the same position for the left pixel
and the right pixel is shown in a graph in the middle. In the
graph, a vertical axis represents the transmittance, and a
horizontal axis represents a distance from the left end of the
pixel. A width of the pixel electrode in the exemplary embodiment
is about 60 micrometers (.mu.m).
[0138] In an exemplary embodiment, as shown in the graph of FIG. 8,
the transmittance is improved on the edge of the pixel electrode,
and the transmittance is also improved near the longitudinal
electrode 191 of the pixel electrode 190 due to the longitudinal
opening 271 of the common electrode 270. As a result, the overall
transmittance may be improved by about 25%.
[0139] Next, the arrangement of the liquid crystal molecules will
be described with reference to FIG. 9.
[0140] FIG. 9 is a view showing an arrangement of liquid crystal
molecules according to a comparative example and an exemplary
embodiment.
[0141] In FIG. 9, the liquid crystal molecules of an exemplary
embodiment are indicated by 305, and the liquid crystal molecules
of the comparative example is indicated by 305-1. Also, in FIG. 9,
the arrangements of the liquid crystal molecule of the comparative
example and the exemplary embodiment corresponding to FIG. 8 are
shown to be overlapped.
[0142] The liquid crystal molecule 305-1 of the comparative example
and the liquid crystal molecule 305 of the exemplary embodiment are
similar at most positions, the angle of the part where the
longitudinal opening 271 of the common electrode 270 is disposed
are substantially different from each other. It may be shown that
the liquid crystal molecule 305 of the exemplary embodiment is
arranged with an angle corresponding to about 45.degree. such that
the transmittance is high, and the liquid crystal molecule 305-1 of
the corresponding part of the comparative example is arranged in a
direction close to the vertical direction such that the
transmittance is low.
[0143] Next, the change of the transmittance characteristic
according to the position and existence of the notch opening 275
will be described with reference to FIG. 10.
[0144] FIG. 10 is a view showing a characteristic change depending
on a change of a notch in a common electrode according to an
exemplary embodiment.
[0145] In FIG. 10, FIG. 10 (C) and FIG. 10 (D) show exemplary
embodiments in which the common electrode 270 only includes the
longitudinal opening 271 for the pixel electrode 190 including the
edge transverse electrode 196, and FIG. 10 (A) and FIG. 10 (B) show
exemplary embodiments in which the common electrode 270 includes
both of the longitudinal opening 271 and the notch opening 275.
[0146] Also, FIG. 10 (B) and FIG. 10 (D) show exemplary embodiments
in which the position of the longitudinal opening 271 is disposed
at the position that does not correspond to the longitudinal
electrode 191 of the pixel electrode 190.
[0147] Overall, as shown in FIG. 10, even if the position of the
longitudinal opening 271 does not correspond to the longitudinal
electrode 191 and is mismatched, the change in the transmittance is
substantially small. However, as shown in FIG. 10, a stain may be
visible.
[0148] In exemplary embodiments without the notch opening 275, as
shown in FIG. 10 (C) and FIG. 10 (D), the transmittance is slightly
increased from 123% to 125%.
[0149] In exemplary embodiments where the notch opening 275 exists,
the arrangement direction of the liquid crystal molecules may be
effectively determined even though four domains overlap each other,
and thus, the liquid crystal molecule may be substantially
stable.
[0150] Next, the characteristic on a side surface will be described
with reference to FIG. 11.
[0151] FIG. 11 is a view showing a luminance change in a front and
a side according to a comparative example and an exemplary
embodiment.
[0152] The front means the front of the liquid crystal panel, and
the case that a viewing angle moves from the front to the long side
direction of the liquid crystal panel means the side. Also, FIG. 11
(A) shows the comparative example, and
[0153] FIG. 11 (B) shows an exemplary embodiment. In the graph of
FIG. 11, the horizontal axis represents the voltage, and the
vertical axis represents the transmittance at the position of 60
degrees of the side. The 100% transmittance is based on the maximum
transmittance at the front of the comparative example.
[0154] As shown in FIG. 11 (A), in the case of the comparative
example, a region where the front transmittance is less than the
side transmittance exists where the voltage is from about 2.4 volts
(V) to about 4 V. In FIG. 11, photographs showing the
characteristic of the side according to the voltage of this part is
added. As shown by the photographs, the light leakage phenomenon
occurs at the side in the comparative example such that higher
transmittance than the front transmittance appears. Also, it may be
shown that the position where the light is leaked is the middle
part.
[0155] As shown in FIG. 11 (B), in an exemplary embodiment, it may
be shown that light is not leaked from the side even at a low gray,
and thus low transmittance is maintained. As a result, in an
exemplary embodiment, gray reversion may not occur on the side.
[0156] Conventionally, when the gray reversion occurs on the side
as in the comparative example, a method of dividing one pixel
electrode into a sub-pixel electrode for displaying a high gray and
another sub-pixel electrode for displaying a low gray to be
recognized with an average of the high and low grays on the side to
removing side gray reversion is typically used. When one pixel
includes two sub-pixel electrodes as described above, at least two
thin film transistors are provided for the one pixel such that the
structure of the pixel may become complicated. Also, when a pixel
is formed in a small area to realize high resolution, such a
structure may not be effectively formed in such a small area for
the pixel.
[0157] In an exemplary embodiment, since the gray reversion does
not occur on the side, one pixel may have a structure including
only a single pixel electrode and a single thin film transistor,
such that the pixel structure may be effectively formed in a small
area to realize high resolution.
[0158] In such an embodiment, as shown in FIG. 11, when a high gray
may be displayed with high transmittance, such that the image of
the high luminance may also be effectively displayed on the
side.
[0159] Next, the angle .PHI. of the liquid crystal molecule on the
side at a predetermined voltage will be described with reference to
FIG. 12.
[0160] FIG. 12 is a view showing an arrangement characteristic of a
liquid crystal molecule depending on a voltage at a specific
position in a comparative example and an exemplary embodiment.
[0161] FIG. 12 (A) shows the comparative example, and FIG. 12 (B)
shows an exemplary embodiment. In FIG. 12, the angle .PHI. of the
liquid crystal molecule at a part indicated by the circle is shown
in each view. In the comparative example of FIG. 12 (A), for
example, when a voltage of 3 V is applied to the pixel electrode,
the angle .PHI. of the liquid crystal molecule at the part
indicated by the circle is 35.degree..
[0162] Referring to FIG. 12 (A), it is shown that the liquid
crystal molecule 305-1 has a substantially constant angle .phi.
regardless of the voltage. Considering that the maximum
transmittance appears when the liquid crystal molecule 305-1 is
45.degree., in the corresponding part, a problem that the
transmittance does not change according to the gray occurs because
the maximum transmittance appears at most of the voltages.
[0163] In an exemplary embodiment, as shown in FIG. 12 (B), the
angle .PHI. of the liquid crystal molecule 305 is increased
according to the applied voltage. In such an embodiment, it the
gray representation is effectively realized on the side.
[0164] The angle .PHI. of the liquid crystal molecule based on the
predetermined position of the pixel electrode has been described
with reference to FIG. 12. Next, the angle .PHI. of the liquid
crystal molecule based on three positions that are different from
each other in one domain of the pixel electrode will be described
with reference to FIG. 13.
[0165] FIG. 13 is a view showing an angle at various positions of a
liquid crystal molecule depending on a voltage in a comparative
example and an exemplary embodiment.
[0166] FIG. 13 (A) shows the comparative example, and FIG. 13 (B)
shows the exemplary embodiment.
[0167] As shown in the arrangement view of the liquid crystal
molecule for 3 V at a bottom of FIG. 13 (A) and FIG. 13 (B), the
angle .PHI. of the liquid crystal molecule depending on each
voltage is shown on three parts (an edge, a middle, a spine) in one
domain.
[0168] In the comparative example, as shown in FIG. 13 (A), the
angle .PHI. of the liquid crystal molecule on the edge, the angle
.PHI. of the liquid crystal molecule on the middle, and the angle
.PHI. of the liquid crystal molecule on the spine adjacent to the
longitudinal electrode 191 are substantially different from each
other for each voltage.
[0169] In an exemplary embodiment, as shown in FIG. 13 (B), the
difference of the angles .PHI. of the liquid crystal molecule on
the edge, the middle and the spine is substantially reduced.
[0170] As shown in FIG. 13, since the transmittance T is
proportional to a square of a value obtained by applying twice the
angle .phi. of the liquid crystal molecule in a sine function, the
stain may be recognized at a specific part in the comparative
example due to substantial difference in transmittance depending on
positions thereof. In the comparative example, when the voltage has
a predetermined value or greater, the transmittance at the spine or
the middle may be limited.
[0171] In an exemplary embodiment, the angle .PHI. of the liquid
crystal molecule is changed depending on the change of the voltage
on the edge, the middle and the spine, thereby changing the
transmittance such that a grayscale may be effectively expressed.
In such an embodiment, the angles .PHI. of the liquid crystal
molecule are similar to each other on the edge, the middle and the
spine at a same voltage such that a stain, which occurs when the
luminances of parts are different from each other, may be
effectively prevented.
[0172] In an exemplary embodiment, the angle .PHI. of the liquid
crystal molecule is also small when displaying the low gray by
providing the low voltage, and the angle .PHI. of the liquid
crystal molecule is large when displaying the high gray by the high
voltage. In such an embodiment, the angle .PHI. of the liquid
crystal molecule is automatically adjusted depending on the voltage
or the gray, as indicated by "Auto-Steering" in FIG. 13 (B).
However, in the comparative example, the change of the angle .PHI.
of the liquid crystal molecule depending on the voltage is not
substantially large such that "Auto-Steering" may not occur.
[0173] The structure of an exemplary embodiment of the pixel
electrode and the common electrode has been described with
reference to FIG. 3 and FIG. 7.
[0174] Next, various exemplary embodiments of the pixel electrode
and the common electrode will be described with reference to FIG.
14.
[0175] FIG. 14 is a view showing a structure of a pixel electrode
and a common electrode according to various exemplary
embodiments.
[0176] In FIG. 14, the structures of various embodiments of the
pixel electrode 190 are shown. In such embodiments, the pixel
electrode 190 includes the longitudinal electrode 191, the
transverse electrode 192 and the branch electrode 193, and the edge
transverse electrode 196 or the edge longitudinal electrode 195 are
additionally provided. The branch electrode 193 may include a part
that is not oblique, and in an exemplary embodiment, the number of
the transverse electrodes 192 or longitudinal electrodes 191 may be
two. In such embodiments, as shown in FIG. 14, the structure of the
common electrode 270 includes both the longitudinal opening 271 and
the notch opening 275.
[0177] First, an exemplary embodiment of FIG. 14 (A) will be
described.
[0178] The pixel electrode 190 of FIG. 14 (A) includes one
longitudinal electrode 191 and one transverse electrode 192, and a
plurality of branch electrodes 193 extending in an oblique
direction therefrom. The edge transverse electrode 196 or the edge
longitudinal electrode 195 is disposed at ends of the plurality of
branch electrodes 193, thereby having a closed structure in which
the ends of the branch electrodes 193 are not open. In such an
embodiment, the edge transverse electrode 196 is not provided at
the branch electrode 193 extending in a lower direction. The edge
transverse electrode 196 disposed at an upper side and the edge
longitudinal electrode 195 disposed at a left side are connected to
each other, however the edge longitudinal electrode 195 disposed at
a right side is not connected to the edge transverse electrode 196
disposed at the upper side. In such an embodiment, the detailed
connection structure may be variously modified.
[0179] The longitudinal opening 271 of the common electrode 270 is
defined at a part thereof corresponding to the longitudinal
electrode 191, and the notch opening 275 is defined corresponding
to a part where the longitudinal electrode 191 and the transverse
electrode 192 cross each other.
[0180] In an alternative exemplary embodiment, as shown in FIG. 14
(B), the edge transverse electrode 196 may be disposed below the
pixel electrode 190. In such an embodiment, the edge longitudinal
electrode 195 disposed at the left side is connected to the edge
transverse electrode 196 disposed at the upper side.
[0181] The structure of FIG. 14 (C) is similar to that of FIG. 14
(B), except that the edge transverse electrode 196 and the edge
longitudinal electrode 195 are disconnected. As shown in FIG. 14
(C), one side end of the transverse electrode 192 extends and is
not connected to the edge longitudinal electrode 195 on the right
side.
[0182] The structure of FIG. 14 (D) includes the edge longitudinal
electrode 195, but does not include the edge transverse electrode
196. As shown in FIG. 14 (D), the branch electrode 193 includes the
part that is not obliquely progressed. That is, the branch
electrode 193 has a structure that extends in the horizontal
direction from the longitudinal electrode 191 and is bent in the
oblique direction. However, according to an alternative exemplary
embodiment, the branch electrode 193 may have the structure that
extends in the oblique direction from the longitudinal electrode
191 and then extends in the vertical or horizontal direction while
being bent.
[0183] FIG. 14 (E) is similar to FIG. 14 (D) except that a
structure thereof further includes the edge transverse electrode
196.
[0184] FIG. 14 (F) shows an exemplary embodiment including two
transverse electrodes 192 in which the longitudinal electrode 191
and the transverse electrode 192 cross each other at two places
such that two notch openings 275 of the common electrode 270 are
defined. In the exemplary embodiment of FIG. 14 (F), the branch
electrodes 193 of the pixel electrode 190 are arranged at different
intervals at different angles. In such an embodiment, a gap or
distance between two adjacent branch electrodes 193 is narrow at
one end and wider at the other end.
[0185] FIG. 14 (G) shows an embodiment having a structure in which
features of the exemplary embodiments of the invention described
above are combined. In such an embodiment, the branch electrode 193
is obliquely formed at a part close to the transverse electrode
192, that is, the upper and lower part of the transverse electrode
192. In such an embodiment, the branch electrode 193 of the bent
structure is disposed at both sides thereof. In such an embodiment,
the uppermost and lowermost branch electrodes 193 have the
structure arranged obliquely without bending again. The edge
electrodes 195 and 196 for each part are disposed to have a closed
structure, and the transverse electrode 192 has a structure in
which an end portion is not further extended to be connected to the
edge longitudinal electrode 195.
[0186] FIG. 14 (H) shows an exemplary embodiment where the pixel
electrode 190 having two longitudinal electrodes 191 and one
transverse electrode 192. In such an embodiment, since there two
places where the transverse electrode 192 and the longitudinal
electrode 191 cross each other, two notch openings 275 are defined
corresponding to the crossed portions. The exemplary embodiment of
FIG. 14 (H) shows a structure without the edge electrodes 195 and
196, but not being limited thereto. Alternatively, at least one
among the edge electrodes 195 and 196 may be included.
[0187] The structure of the pixel electrode 190 shown in FIG. 14
merely shows some exemplary embodiments of the invention, and the
invention is not limited thereto. Such embodiments may be variously
modified by combining the features described above.
[0188] FIG. 14 shows a structure of the common electrode 270 in
exemplary embodiments. In such embodiments, the common electrode
270 includes the longitudinal opening 271 and the notch opening 275
having a rhombus shape.
[0189] However, the structure of the common electrode 270 may also
be variously modified. A structure of the common electrode 270 in
exemplary embodiments will be described with reference to FIG.
15.
[0190] FIG. 15 is a view showing a structure of a common electrode
according to various exemplary embodiments.
[0191] FIG. 15 (A) shows an exemplary embodiment, where the common
electrode 270 has a structured described above. The notch opening
275 of FIG. 15 (A) may have one of various shapes such as a
rhombus, a circle, or an octagon.
[0192] In an alternative exemplary embodiment, as shown in FIG. 15
(B), the common electrode 270 may not include the notch opening
275.
[0193] FIG. 15 (C) shows another alternative exemplary embodiment
where the notch opening 275 of the common electrode 270 may have a
longer elongated shape. In such an embodiment, the notch opening
275 may extend in the horizontal direction, and may be disposed at
the position corresponding to the transverse electrode 192 among
the pixel electrode 190. The notch opening 275 shown in FIG. 15 (C)
may have a structure extending from the part where the transverse
electrode 192 and the longitudinal electrode 191 cross each other
and extending to a predetermined position of the transverse
electrode 192.
[0194] Hereinafter, features of an exemplary embodiment having the
above-described pixel structure will be described in detail.
[0195] FIG. 16 is a view showing light leakage in an upper side for
an arrangement of a liquid crystal molecule according to an
exemplary embodiment, and FIG. 17 is a view showing a
characteristic depending on a position for an arrangement of a
liquid crystal molecule according to an exemplary embodiment.
[0196] As shown in FIG. 13 (B), in an exemplary embodiment, the
angle .PHI. of the liquid crystal molecule may be small when a low
voltage is applied to the pixel electrode.
[0197] FIG. 16 shows the case that the angle .PHI. of the liquid
crystal molecule 305 is arranged to be small, and a case that the
user views the liquid crystal molecule 305 from a side and from
above.
[0198] When the angle .phi. of the liquid crystal molecule 305 is
small, when the user views the liquid crystal molecule 305 from a
side, there is no light leakage phenomenon since one end of the
liquid crystal molecule 305 is seen, however, when viewed from
above, the light leakage phenomenon may occur since a side of the
liquid crystal molecule 305 is seen.
[0199] As shown in the graph at the bottom of FIG. 16, when the
voltage of 3 V is applied, the transmittance is low when viewed
from a side (a horizontal side view), such that light leakage may
not occur. However, when from an upper side (a vertical side view),
the transmittance is high such that light leakage may occur.
[0200] In an exemplary embodiment, the degree of transmission is
measured depending on the angle of the side surface may be as shown
in FIG. 17.
[0201] FIG. 17 shows a result (A) with a shape close to the circle
and a result (B) with a shape similar to the shape of letter "8".
Each result is a line connecting the transmittance at a certain
angle. Herein, the (B) result is also referred to as an 8-shaped
luminance distribution.
[0202] First, the result (A) is obtained by measuring the
transmittance at various angles in the case of the comparative
example, where the transmittance is relatively large at the upper
side and the lower side, and the transmittance is substantially
uniform.
[0203] In an exemplary embodiment, as shown by the result (B), the
transmittance is low while being concave while viewing from the
right and left sides, and the transmittance is very high in the
upper side and lower side. When a low voltage is applied to display
the low gray, the high transmittance due to the light leakage at
the upper and lower side views may be undesired.
[0204] In an exemplary embodiment, as described above with
reference to FIG. 2, the prism hill is oriented toward the light
guide and the extending direction of the prism hill is formed in a
same direction as the short side direction of the liquid crystal
panel (i.e., the length direction of the pixel electrode or the
extending direction of the data line).
[0205] The structure of such a prism sheet 420 has the
characteristic of transmitting light to the left and right, thereby
preventing light from being transmitted to up and down.
[0206] FIG. 18 shows the characteristic of the light passing
through the backlight unit when such a prism sheet 420 is
included.
[0207] FIG. 18 is a view showing a characteristic of light provided
from a backlight unit of a liquid crystal display according to an
exemplary embodiment.
[0208] Generally, the light provided from the backlight to the
liquid crystal display represents a constant luminance of a
circular shape (also referred to as a circular luminance
distribution) since there is no directionality. In an exemplary
embodiment, as shown in FIG. 18, the light provided from the
backlight to the liquid crystal display may have relatively high
luminance on the left and right sides and relatively low luminance
on the upper and lower sides, thereby the luminance is displayed in
an elliptical shape spread widely to the left and right
(hereinafter, referred to as an elliptical luminance distribution)
because the prism sheet 420 is oriented in a way such that the
prism hill faces the light guide and the extending direction of the
prism hill is arranged in a same direction as the length direction
of the pixel electrode (i.e., the extending direction of the data
line).
[0209] Hereinafter, the characteristics of light emitted from the
backlight unit of the comparative example and the backlight unit of
an exemplary embodiment will be described with reference to FIG.
19.
[0210] FIG. 19 is a view showing characteristics of a prism sheet
according to a comparative example and characteristics of a prism
sheet according to an exemplary embodiment.
[0211] FIG. 19 shows the characteristics of light emitted from the
backlight according to the exemplary embodiment (a reverse prism)
and the comparative example (a cross prism). In the case of the
comparative example, the prism hill is disposed toward the display
panel, two prism sheets are used, and the extending directions of
prism hills of the two prism sheets are perpendicular to each
other. In such a structure, since the extending directions of the
prism hill are two directions perpendicular to each other, the
light spreads not only in left and right directions, but also in up
and down directions. As a result, unlike FIG. 18, the light has a
circular luminance distribution.
[0212] FIG. 19 (A) shows a light amount in the direction
perpendicular to the extending direction of the prism hill in an
exemplary embodiment (the reverse prism), that is, in the side
surface. As shown in FIG. 19 (A), in an exemplary embodiment, a
half width, that is, the width of the part having the light amount
of 50%, is 18.degree. (the angle of one side is 9.degree. such that
the angle of both sides is 18.degree.). As compared with the case
of the comparative example (the cross prism or C prism), the half
width is small by about 19.degree., which is smaller by 38.degree.
as a whole.
[0213] FIG. 19 (B) shows the light amount viewed from the same
direction as the extending direction of the prism hill of the
exemplary embodiment (the reverse prism or R prism), that is, from
the upper side or the lower side, and such light amount may be
substantially the same as that of the comparative example (C
prism).
[0214] This is because the characteristic has the elliptical
luminance distribution due to the prism sheet 420.
[0215] The characteristic an exemplary embodiment including the
prism sheet 420 and the pixel structure described above will be
described in greater detail with reference to FIG. 20.
[0216] FIG. 20 is a view showing a characteristic that is changed
by using a prism sheet according to an exemplary embodiment.
[0217] FIG. 20 (A) shows the luminance distribution of the "8"
character shown in FIG. 17 as the luminance distribution depending
on the angle in an exemplary embodiment.
[0218] FIG. 20 (B) shows luminance distribution compensated by the
prism sheet 420 in an exemplary embodiment is shown in.
[0219] FIG. 20 (B) shows a near-circular luminance distribution at
the center, which corresponds to a combination of the luminance
distribution by the prism sheet 420 and the luminance distribution
of FIG. 20 (A). That is, the prism sheet 420 has the luminance that
is concave in the side, in which light is provided laterally by the
prism sheet 420, such that a higher luminance appears. On the other
hand, in FIG. 20 (A), the high luminance due to the light leakage
of the upper and lower sides is reduced because less light is
provided to the upper and lower sides by the prism sheet 420,
thereby displaying a relatively lower luminance.
[0220] In an exemplary embodiment, as described above, the prism
sheet 420 is oriented in a way such that the prism hill faces the
light guide and the extending direction of the prism hill is the
same as the length direction of the pixel electrode (i.e., the
extending direction of the data line), and, the compensation
thereby occurs in the pixel having the pattern of the pixel
electrode and the pattern of the common electrode described
above.
[0221] Next, the luminance distribution of the light depending on
each position of the display device will be described with
reference to FIG. 21. Particularly, the change of the luminance
distribution of the light by the diffusion layer 330 will be
described in detail.
[0222] FIG. 21 is a view showing a characteristic of light at each
position of a liquid crystal display according to an exemplary
embodiment.
[0223] FIG. 21 schematically shows the liquid crystal display shown
in FIG. 2. FIG. 21 further shows that the light source 410 is
supported behind the light guide 400, and a light source substrate
411 for supplying a power to the light source 410 is additionally
shown. FIG. 21 further shows that the liquid crystal display may
further include a case 500 such as a chassis to receive the display
panel and the backlight unit together.
[0224] FIG. 21 respectively shows the luminance distribution
passing through the light guide LGP 400, the luminance distribution
passing through the prism sheet 420, and the luminance distribution
of the light emitted from the liquid crystal display
(LOP/Panel).
[0225] First, the light incident on the prism sheet 420 after
passing through the light guide 400 is shown in FIG. 21 (A). The
light from the light guide 400 is incident on the prism sheet 420
with the similar luminance distribution to the circular shape.
[0226] The luminance distribution of the light emitted after being
incident to the prism sheet 420 (e.g., R. Prism) is shown in FIG.
21 (B). As shown in FIG. 21 (B), the light spreads to the left and
right by the prism sheet 420 and does not spread vertically,
thereby having an elliptical luminance distribution in the
side.
[0227] The light emitted from the prism sheet 420 is recognized by
the user through the lower polarizer 310, the display panel 100,
the upper polarizer 320 and the diffusion layer 330. The luminance
distribution of the light emitted through the diffusion layer 330
is shown in FIG. 21 (C).
[0228] In the luminance distribution of FIG. 21 (C), the luminance
increases at the upper side and the lower side compared with the
luminance distribution of FIG. 21 (B). This is because the
diffusion layer 330 in the exemplary embodiment may have a
characteristic of diffusing the light in the up and down
directions. In such an embodiment, the prism sheet 420 transmits
the light in the right and left directions such that the light is
decreased in the up and down directions. However, in such an
embodiment, the light in the up and down directions is compensated
and displayed since the diffusion layer 330 is diffused in the up
and down directions.
[0229] FIG. 21 shows an exemplary embodiment in which the light
source 410 is disposed at one side of the light guide, but not
being limited thereto. Alternatively, the light source 410 may be
disposed under the display panel (a directly below structure). When
the light source 410 has the directly below light source, a hole
may be defined in the reflection sheet 430 and the light source may
be disposed in the hole. In such an embodiment, a lens may be
additionally provided on the light source. In such an embodiment
having the directly below structure, the characteristic of the
light provided to the prism sheet 420 does not change
significantly, and the luminance distribution shown in FIG. 21 may
be applied.
[0230] While the invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
* * * * *